<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
	</body>
</html>

<script type="text/javascript">
	const map = new Map([
		['username', '张三'],
		['age', '20']
	]);
	
	let username = map.get('username');
	console.log(username);
	console.log(map.size);
</script>
